Mediastinal metastatic melanoma: an unusual case presentation of recurrent melanoma

Mediastinal malignant melanoma is rare as both primary and metastatic lesions. We present the case of a 50-year-old man with diagnosis of recurrent melanoma of the mediastinum. Our patient was previously treated for cutaneous melanoma in 2001 with surgical excision. He presented with symptoms of exertional dyspnoea, dull chest pain and non-productive cough for 12 weeks. CT revealed a large heterogeneously enhancing mass, measuring 10.7×7.6 cm, centred within the aortopulmonary window which abutted the adjacent pericardium. Open biopsy of the epicardial mass was performed via left anterior thoracotomy. Immunohistochemical stains performed on the mass were positive for CD99, focally positive for CD56, SOX10, S100 and WT-1. A diagnosis of metastatic melanoma was established. The patient was started on pembrolizumab with pending BRAF testing. V600E and V600K mutations in exon 15 of the BRAF gene were codetected, and the patient was treated with dabrafenib and trametinib.